This invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium containing an fungicide in both of the magnetic layer thereof and at least one of the backing layers provided onto the opposite side of the support tnereof to the magnetic layer.
Generally speaking, a magnetic recording medium comprises a magnetic layer formed by coating over a support such as polyethyleneterephthalate film with a magnetic paint prepared by mixing and dispersing magnetic powders in binders, and then by drying it.
Such magnetic recording media are popularly used in the fields of audios, videos. computers and the like in the forms of magnetic tapes, magnetic disks, magnetic sheets, floppy disks and the like.
In the magnetic recording tapes used for the above-mentioned purposes the surface of the magnetic recording layer is smoothly finished in general, with the purpose of improving the sensitivity, especially the output from a high frequency region. Such smooth-surfaced magnetic recording tapes are apt to be wound up irregularly, because the tapes are not properly taken up when taking up or rewinding. If using an irregularly wound magnetic recording tape such as mentioned above, there causes a defect that the tape runnability is worsened and the output is fluctuated, because of the variation of the tension. In addition to the above, tapes are apt to be deformed and damaged. To avoid the abovementioned defects, there has been proposed a magnetic recording tape provided a backing layer over to the opposite surface of a support to a magnetic recording layer.
Such backing layer is also effective to reduce frictional resistance between tapes or to improve tne charging properties.
To serve as the binders of the above-mentioned magnetic layer and backing layer, a thermoplastic resin or thermosetting resin such as synthetic resins including, for example, a vinyl chloride-vinyl acetate copolymer resin, a cellulose derivative, an epoxy resin, a polyvinyl outyral, a polyurethane resin, a synthetic rubber resin, an acryl resin, a polyester resin, and the like. However, on the surface or inside of the magnetic layer and backing layer each formed oy using the above-mentioned synthetic resins to serve as the binder, microorganisms such as fungus (e.g., Aspergillus penicilloides, Chaetomium globosum, Cladosporium herbarum, Trichoderma sp. and the like) are apt to be produced. Inter alia, binders made of polyurethane resin are apt to produce microorganisms (i.e., fungus), and if such microorganisms are produced in a magnetic layer, there causes undesired troubles such as a delamination of the magnetic layer caused by adhering to each other tape, contamintion of a recording head, impediment to the tape flatness, erroneous signal of tapes or disks, and the like. If such microorganisms are produced in a backing layer, a tape which was taken up adheres to each other side so as not to separate and is apt to be torn when the microorganisms are grown up.
Fungus which peeled off from a tape may contaminate a magnetic head or damage the smoothness of the tape because of adhering to the surface of the tape. Tapes are used in great numbers for personal hobby and industrial purposes, and among them, there are some tapes which are desired to preserve for a long time as valuable collections and required to have a high reliability to serve as an external recording medium for a computer. It is, therefore, eagerly desired to take a countermeasure to prevent the damages caused by getting fungus.
Accordingly, various countermeasures have been proposed with the purpose of preventing fungus to the utmost, and some of them have actually been put in practice. For example, Yamano, `Journal of Antibacterial and Antifungal Agents, Japan` 4[10], 487 (1976) describes the improvement of environmental conditions, the selection of synthetic resin materials and the method of using chemicals for preventing fungus. However, such proposals have not been applied to any magnetic recording medium and have also lacked the feasioility. Especially, the selection of chemicals are difficult to prevent such a microorganisms as fungus and the like because of tne magnetic property, durability, drop-out and the like. It is the state of things that any of the suitable chemicals has still not been found to use.
It is an object of the invention to provide a magnetic recording medium getting no or relatively less microorganisms such as fungus with the use of an fungicide.
Another object of the invention is to provide a magnetic recording medium which is excellent in durability, from which microorganisms such as fungus are reduced or got rid of.
A further object of the invention is to provide a magnetic recording medium displaying an excellent magnetic property, from which the microorganisms such as fungus are reduced or got rid of.
Yet another object of the invention is to provide a magnetic recording medium containing the fungicide which is high in safety to human body.
A still further object of the invention is to provide a magnetic recording medium whose magnetic layer and backing layer do not adhere to each other when the magnetic recording medium is taken up.
An additional object of the invention is to provide a magnetic recording medium which is properly taken up when being wound and rewound and is excellent in running stability.